Why do vertical extension bids come in low in Borama?

A low bid on a vertical extension in Borama usually means the estimator priced a new floor standing on its own and left out the work that ties it to the building underneath. On many vertical extensions the risk in an underbid sits in the connections: the existing footing, the column starters, the slab edge. The bid looks clean because the omissions are invisible until the roof is opened.

Why does the existing building make the bid uncertain?

Nobody can price the junction until someone exposes it. An estimator working from a drawing alone sees a column grid, not the reinforcement that actually left the old slab. General practice is to expose the top of a column, chip back cover at a slab edge and check starter bar diameter, spacing and lap length against the drawing, then photograph the opening and log it. Confirm the exposure method and made-good detail with the project engineer first.

The same gap applies to the ground under the new columns. If the extension loads a footing that was sized for one floor, the estimator needs the original foundation drawing or a trial pit beside the existing base. Have the footing exposed and logged so the ground under the new columns is established on site, not assumed from a drawing. Ask the municipal engineer's office whether it holds borehole logs or approved drawings for the plot, and request any test records the original builder kept. Where nothing exists, price the investigation as a separate item so the bidder is not guessing.

Which omitted costs push a vertical extension bid down?

Low bids drop the items that only appear once work starts. The list repeats across projects:

• Temporary propping and shoring of the existing slab edge while the new columns are cast.
• Breaking out and re-forming the roof slab, parapet and any waterproofing the extension crosses.
• Rebar couplers or drilled and grouted starters where no bars were left.
• Load testing or extra investigation when the existing footing capacity is unknown.
• Haulage and disposal of demolition arisings.
• Working at height: edge protection, a hoist or crane time, and the slower output that comes with it.
• Reinstating finishes, services and drainage disturbed by the new structure.

Each one is real work. A bidder who leaves them out is not necessarily dishonest; the tender documents may never have asked for them. General practice is to require a priced schedule of these items and to compare bidders line by line, not on the total. Confirm which items the project specification makes the contractor's responsibility.

How do you test a low bid before you sign?

The cheapest way to test a bid is to ask the bidder to price the junction. Send every bidder the same written list of omitted items and ask for a rate against each, with the assumption stated. A bidder who cannot produce a rate has not thought about the connection.

Then ask a supervisor on a comparable extension to describe what typically changed once the roof was opened, what the original estimate missed and how it was settled. That conversation gives a client a realistic picture of how much a vertical extension bid can move once the existing structure is exposed. For the tender itself, check what the contract allows on variations and on access to the site before award, so an omitted item is handled in writing rather than argued on site. If a bid still sits well below the others after the same list has been priced, the gap is often in the connection work, and the client carries it later.

What to do next

Before you award, send every bidder one written list of the tie-in items and ask for a rate against each with the assumptions stated. Ask the municipal engineer's office what records it holds for the plot, then expose one column top and one footing edge, and photograph the result. Compare the returned rates, not the totals.